The present invention relates to a LCD (Liquid Crystal Display), more particularly, to a driving circuit and driving method for a LCD.
LCDs have many pixels arranged in rows and columns in their screen. Each pixel has its own electrode, i.e. pixel electrode, for applying a voltage to a liquid crystal material in that pixel. By selecting a row of pixels, the voltages are applied to the pixel electrodes in the selected row through column signal lines. Selecting all the rows sequentially, all the pixel electrodes in the screen are supplied with their own voltages. Through these voltages, the liquid crystal material in each pixel is driven and changes its orientation, thereby the amount of light passing through each pixel is controlled so that an image is displayed on the screen.
Meanwhile, it should be noted that LCDs typically have a common electrode which is commonly owned by all pixels, and to be precise, the voltage difference between the pixel electrode and the common electrode is applied to the liquid crystal material in the pixel to control the amount of passing light.
The time required for selecting all rows, i.e. all pixels in the screen, is referred to as xe2x80x9cOne field periodxe2x80x9d, and a voltage applied to the liquid crystal material in each pixel is refreshed once in the xe2x80x9cone field period. Of course in a case there is no need to change the displayed image in a pixel, the same voltage is again applied to that pixel.
Though a LCDs, which are lightweight, lower power consumption and display exquisite images, are used widely replacing the conventional CRT displays, there is a shortcoming of lower displaying quality for moving images.
As mentioned above, LCDs can display images by controlling the amount of passing lights through the orientations of liquid crystal material. Thus, when an image with motion is displayed, i.e. displayed image must be changed, the orientation of liquid crystal material must be changed by changing voltages applied to them. However, it requires relatively long time for a liquid crystal material in certain orientation to be changed into another orientation according to the newly applied voltage. Therefore, in case of displaying object which moves at high-speed, there is a problem which causes afterimage and blurred image since the liquid crystal material can not reach the desired orientation during the xe2x80x9cone field periodxe2x80x9d.
Therefore, an object of the present invention is to provide a driving circuit and a driving method for LCD having high displaying quality for moving images by accelerating response of liquid crystal material.
Another object of the present invention is to provide a driving circuit and a driving method for LCDs which can obtain high displaying quality for moving images with accelerating response of liquid crystal material within a limited memory and circuit scale.
In order to achieve the above mentioned objects, a driving method for driving LCD according to the present invention is characterizing in that a voltage applied to a pixel to drive liquid crystal material in the pixel is determined with a supplied current field image data which is designating the desired transparency of the pixel in the current field and the voltage applied to the pixel in the current field is determined as a voltage with which the transparency of the pixel at the end of the current field becomes the designated transparency.
A driving method for driving LCD according to the present invention is characterizing in that a voltage applied to a pixel in the current field is determined with the current field image data and a preceding field image data which are designating the desired transparency of the pixel in the current and preceding field, and the voltage applied to the pixel in the current field is determined as a voltage with which the transparency of the pixel at the end of the current field becomes the designated transparency.
And, a driving circuit for LCD according to the present invention comprises a frame memory in which a current field image data is stored and retrieved as a preceding field image data after delay of one field period, a data table for quick response in which output data is stored in correspondence with possible value of a preceding field image data and possible value of a current field image data, and a processor for determining an output data from the current field image data and the preceding field image data using the data table for quick response.
The driving circuit according to the present invention comprises a frame memory in which the current field image data is stored and retrieved as a preceding field image data after delay of one field period, a data table for quick response in which output data is stored in correspondence with some of the possible value of the preceding field image data and some of the possible value of the current field image data, and a processor for determining an output data from the current field image data and the preceding field image data using the data table for quick response.
A driving circuit for LCD according to the present invention further comprises a converting means which convert the bit length of the current field image data, a frame memory in which the current field image data is stored and retrieved as the preceding field image data after delay of one field period, the data table for quick response in which output data is stored in correspondence with some of the possible value of the preceding field image data and some of the possible value of the current field image data, and the processor for determining an output data from the current field image data and the preceding field image data using the data table for quick response. The number of the possible preceding field image data on the data table preferably equals to the number represented with bit length of the preceding field image data.
The driving circuit for LCD according to the present invention comprising the frame memory in which a current field image data is stored and retrieved as a preceding field image data after delay of one field period, the data table for quick response in which output data is stored in correspondence with some of the possible value of a preceding field image data and some of the possible value of a current field image data, a differential data table in which differential data is stored in correspondence with the some of the possible value of a preceding field image data and the some of the possible value of a current field image data, and a processor for determining an output data from the current field image data and the preceding field image data using the data table for quick response and the differential data table.
The driving circuit for LCD according to the present invention comprising the converting means which convert the bit length of the current field image data, the frame memory in which a current field image data is stored and retrieved as a preceding field image data after delay of one field period, the data table for quick response in which output data is stored in correspondence with some of the possible value of a preceding field image data and some of the possible value of a current field image data, the differential data table in which differential data is stored in correspondence with the some of the possible value of a preceding field image data and the some of the possible value of a current field image data, and a processor for determining an output data from the current field image data and the preceding field image data using the data table for quick response and the differential data table. The number of the possible preceding field image data on the data tables preferably equal to the number represented with bit length of the preceding field image data.
In the driving circuits for LCD according to the present invention, a voltage applied to a pixel during the current field to drive liquid crystal material in the pixel is preferably determined by the output data so that the transparency of the pixel at the end of the current field becomes the transparency designated by the current field image data.
The driving method for driving LCD according to the present invention, in which an output data is determined from preceding field image data and current field image data using a data table for quick response storing output data in correspondence with the preceding field image data and the current field image data, and a voltage corresponding to the output data is applied to a pixel to drive liquid crystal material in the pixel, comprises the steps of retrieving four output data defined with two preceding field image data and two current field image data which are closest to the preceding field image data and the current field image data respectively from the data table, and determining the output data corresponding to the preceding field image data and the current field image data by linear interpolation using the four output data.
In the method for driving LCD above described, the output data corresponding to the preceding field image data and the current field image data may be determined by linear interpolation using three of the four output data.
The driving method for driving LCD according to the present invention, in which an output data is determined from preceding field image data and current field image data using a data table for quick response storing output data in correspondence with the preceding field image data and the current field image data, and a voltage corresponding to the output data is applied to a pixel to drive liquid crystal material in the pixel is characterized in that the number of the possible preceding field image data on the data table equals to the number represented with bit length of the preceding field image data, two output data defined with the preceding field image data and two current field image data which are closest to the current field image are retrieved from the data table, and the output data corresponding to the preceding field image data and the current field image data is determined by linear interpolation using the two output data.
The driving method for driving LCD, wherein a preceding field image data which is obtained through converting bit length of an image data of preceding field, a current field image data, and a converted current field image data which is obtained through converting bit length of the current field image data are employed to determine an output data, and voltage corresponding to the output data is applied to a pixel to drive liquid crystal material in the pixel, comprises the steps of retrieving an output data defined with the preceding field image data and the converted current field image data from a data table for quick response, retrieving a differential data defined with the preceding field image data and the converted current field image data from a differential data table, multiplying the retrieved differential data by a difference between the current field image data and the converted current field image data, and adding the multiplied differential data and the retrieved output data to obtain the output data.
In the driving methods for LCD according to the present invention, the voltage applied to the pixel is preferably determined by the output data so that the transparency of the pixel at the end of the current field becomes the transparency designated by the current field image data.